This is important first of all because these names will persist across mail server upgrades. If we change mail server hardware, these DNS names will remain. It is also important in the case of SSL IMAP and POP3 because if you do not use these names specifically (like using the generic name 'mail.cs.princeton.edu' instead for instance) then your mail reader will probably complain about a certificate not having the proper identification.

For security reasons only hosts that are registered on the CS network (your-hostname.cs.princeton.edu) can send outbound email via smtp.cs.princeton.edu without authenticating. All other users must use SSL and authenticate to the server in order to send email to recipients outside the department.

Most modern email clients are capable of SMTP Authentication and SSL. Configuration details will vary by client, but the credentials you need will be your Unix username and password, the same as for reading email using IMAP or POP.

We may be limited in what we can do to help you, but the first step would be to email us the message with all headers intact. We might be able to block the sender or host at our mail server but it depends on several variables.

Yes. The reason you're seeing this is because the security certificate being presented to your client is one that we have generated ourselves, and not from a recognized authority (like Verisign). In order for this message to go away, you need to tell your client to treat our certificate as coming from a valid authority (that is, you trust us). To do that, you can go to this page.

For some time now, the CS Department email servers have been using proper SSL certificates that should work normally with most browsers and email clients. If you are still seeing certificate warnings, please contact CS Staff for help investigating further.

Many ISPs are now blocking or intercepting connections on port 25 in order to attempt to reduce spam coming from their networks. To work around this, change the Outgoing (SMTP) port number in your client to 587. This should, in most cases, allow you to connect directly to our server so that TLS and authentication will work as expected.

There are a few possibilities for why you may not be able to receive email. Here are some things to check:

Are you using IMAP or POP over SSL? - For some time now, the CS Department mail service has required using IMAP or POP over SSL to read email. We no longer provide NFS access to the /var/mail spool directory. For help configuring a mail client, see the CS Guide IMAP or POP pages.

Is anyone else receiving email? - If you have verified that you are using IMAP or POP properly, and you are confident that you are not over quota, then it is possible that there is a general email outage. Check the CS Guide main page for scheduled downtime or other information.

In the above example, username@email!address.com was an address that is no longer in use, so the system at email!address.com sent a message explaining that the email was not received.

As an analogy, this is similar to someone going to the post office, sending a letter to a non-existent location and putting your address as the senders. When the post office finds out that the letter cannot be delivered to the intended recipient, the letter will be returned to you, since your address was listed as the sender.

There are various reasons why these types of emails are coming into your Inbox but the most likely reasons are:

1. Someone has "spoofed" your email address, making it look like the email originally came from you. This is a popular tactic that spammers use to send their spam emails. If any of the spam messages are sent to an address that doesn't exist, the email is bounced back to your account, since the spammer made it appear as though the email originated from you. In these cases, there is not much you can do to completely eliminate the problem because the spammer has simply guessed your email address and has inserted it into the From: field, making it look like these emails are coming from you.

2. Another possible reason for getting these emails is that a virus and/or worm may have infected your system. Make sure to update your anti-virus and firewall software and run a full system scan. If you do not have an anti-virus or firewall program installed on your computer, you can take advantage of the free Sysmantec Virus Software offered to all Princeton University Students, Faculty, and Staff (visit http://helpdesk.princeton.edu/kb/display.plx?ID=3308 to install or for more information).

3. If you're certain that your PC does not have a virus, the more likely scenario is that an email virus and/or worm may have infected one or more of your friends' computers, and these people probably have your email address in their address book. The virus tries to spread itself by sending messages to many other users, using the address book of the infected computer. The virus/worm will often use a false address (yours) as the Reply-to: or From: address. If any of the messages that the virus sends bounce back, you will receive that message.

Our email servers perform backups nightly starting at 01:00 and running until they complete. The end time varies based on which accounts are being backed up, as each account is backed up once per week. As each account is backed-up, it is temporarily brought offline so access is suspended. The actual downtime for each account depends on the amount of data to be backed-up, and can vary from a few minutes to a couple of hours for the largest accounts. By performing backups in an offline mode, we ensure maximum integrity of the backed-up data.

Once logged in, click the "Preferences" tab at the top of the screen. Within this tab, you can change many details about your email delivery and presentation. For email forwarding, click on the "Mail" section within Preferences, scroll down to the "Receiving Messages" section and find "Forward a copy to". Enter your forwarding address in the text box, and optionally check the "Don't keep a local copy of messages" box if you wish the email to only be forwarded rather than also delivering it locally.

Once logged in, click the "Preferences" tab at the top of the screen. Within this tab, you can change many details about your email delivery and presentation. For a vacation message, click on the "Out of Office" section in the left-side navigation pane. Check the "Send auto-reply message" option, and set your auto-response message. You can also optionally set start and stop dates for the message. This will allow you to setup a vacation message before your departure that only begins sending auto-responses once your vacation starts, and stops automatically at the end date.